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In this article, Bi1–xCoxFe0.8Mn0.2O3 (BCFMO) nanoparticles with x = 0.0, 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30 were synthesized at 650°C and annealed for 1 h by the sol–gel method. Then, the structural, magnetic, dielectric, and optical properties of BCFMO nanoparticles were investigated with the substitution of cobalt and manganese elements for bismuth and iron under various percentages. X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and ultraviolet (UV)–visible spectrophotometer were used to characterize the prepared samples. By using LCR meter, the dielectric constant ( $\varepsilon ^{\prime }$ ), the dielectric loss factor (tan $\delta$ ), the dielectric loss ( $\varepsilon ^{\prime \prime }$ ), and the electrical conductivity amounts of ac ( $\sigma _{\mathrm {ac}}$ ) for BCFMO nanoparticles were measured at the annealing temperature of 650°C for 1 h in the frequency range of 100 Hz–5 MHz.

PbFe12-xNixO19 nanoparticles (x = 0-1) were prepared by a sol–gel method. The influence of Ni2+ substitution on structural, magnetic and dielectric properties of PbFe12O19 nanoparticles was investigated. The samples of PbFe12-xNixO19 nanoparticles have been characterized by the X-ray diffractomere (XRD), Fourier transform infrared spectrometer (FT-IR), scanning electron spectrometer (SEM), vibrating sample magnetometer (VSM), and an LCR meter. The results reveal that PbFe12-xNixO19 compounds up to x = 0.2 are single phase. The bands of absorption in the 400– 500 cm-1 and the bands of absorption in the range of 500 -600 cm-1, corresponding to the formation of octahedral and tetrahedral sites which confirms the presence of metal– oxygen stretching band in ferrites. Also, SEM images show that by increasing Ni2+ doping grains size have been increased. However, for x > 0.2, the secondary Ni spinel ferrite (NiFe2O4) appears which the saturation magnetization and magnetic coercivity decreases. In addition, Ni2+substitution reduces the dielectric constant, dielectric loss, and ac electrical conductivity for all samples decrease rapidly with increasing applied field frequency and reaches a constant value beyond a certain frequency which this is characteristic of the normal dielectric behaviour of ferrites and has been investigated by Maxwell–Wagner’s two-layer model and Koop’s theory. The variation in ac conductivity (σac) with frequency shows that the electrical conductivity in these ferrites is mainly attributed to the electron hopping mechanism.Therefore; all single-phase Ni2+ substituted samples are suitable for use in magnetic recording media and microwave devices.

In this study, we report the synthesis of tin disulfide/reduced graphrene oxide (SnS2/RGO) nanocomposites by a simple one-step hydrothermal method. In order to investigate the effect of RGO on the structure and optical properties and photocatalytic activity of the products a series of nanocomposites was prepared with different concentrations of GO. The samples were examined using X-ray diffraction, field emission scanning electron microscopy (FESEM), Raman spectroscopy, UV–Vis spectroscopy and photoluminescence techniques. The results confirmed the growth of SnS2 with the hexagonal phase. FESEM analysis showed that the hexagonal tin disulfide nanoplates are uniformly dispersed on the surface of the graphene oxide sheets. The optical examination of SnS2 and SnS2/RGO nanocomposites indicated that the band gaps of all nanocomposites are greater than that of SnS2 due to the quantum confinement effect. The photocatalytic activity of the SnS2/RGO nanocomposites was investigated for degradation of the acid orange 7 dye under visible light. It was observed that all nanocomposites have a higher photocatalytic activity for the degradation in comparison with pure SnS2. The optimum concentration of GO in SnS2/RGO nanocomposite for achieving the highest photocatalytic efficiency (81%) was determined as 2 mg ml−1 during 180 min.

In this study, Zinc hydroxystannate/tin dioxide/reduced graphene oxide (ZnSn(OH)6/SnO2/rGO) ternary nanocomposites were synthesized via a facile one-step hydrothermal route by using graphene oxide, zinc nitrate hexahydrate, and tin (IV) chloride pentahydrate as the precursors. The crystal structure, morphology, and optical properties of ZnSn(OH)6/SnO2/rGO ternary nanocomposites were characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Raman spectroscopy and UV–vis spectroscopy, respectively. The results of XRD pattern revealed the formation of fcc perovskite ZnSn(OH)6 (ZHS) and tetragonal SnO2 structure. The FESEM images displayed that the ZHS microcubes and SnO2 nanoparticles were distributed on the graphene sheets. The composites were used as photocatalyst for degradation of methylene blue (MB) molecules. The photocatalytic performance of the samples showed that the ZHS/SnO2/rGO nanocomposite exhibited a much higher photocatalytic activity than pure samples. The ternary nanocomposite synthesized at 160 °C with a graphene oxide concentration of 1 mg/mL has the ability to completely degradation MB in less than 60 min under UV radiation. The rate of hydroxyl radical (·OH) generated in the photocatalytic process was investigated using PL spectroscopy and coumarin (COU) as a probe molecule. Thus it can be intended that the mechanism of MB degradation by the as-synthesized nanocomposites followed indirect oxidation of the dye by ·OH generated during the photocatalyst process.

In this study, Bi 1.64 Pb 0.36 Sr 2 Ca 2 − x Cd x Cu 3 O 10 superconductors with Cd contents of x = 0.00, 0.01, 0.02, 0.03, 0.04, 0.06, 0.10 and 0.20, were synthesized by a sol-gel method, and the effect of Cd doping, annealing time, ac magnetic fields and frequencies on the ac magnetic susceptibility were studied. The structure and morphology of the samples have been characterized by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The temperature dependence of the ac magnetic susceptibility of the samples was measured as a function of the ac magnetic field amplitude and frequency by an ac susceptometer. The results of the XRD indicated that the Bi-2223 phase increases in the samples, and the ac magnetic susceptibility shows that the weak links between the grains of the samples are improved. The best amount of doping was found to be x = 0.02, which improves the superconducting properties of this system.